Caution
Wet insulation means water or damp air is reaching the loft. Find out whether it is a leak or condensation before you replace anything.
A leak at the bottom corner of a roof window is usually the flashing or a seal, not the glass. Check whether it is condensation first.
A leak on a new roof is the roofer's to put right. Photograph it, tell them in writing, and do not let anyone else work on it first.
High risk
A roof that has visibly dipped needs a structural opinion. Watch whether it is moving and do not load the roof or the ceiling below.
Rot in roof timbers always has a water source. Stop the water first, then cut out and replace the rotten timber. Dry rot is a specialist job.
Describe the job and get a fixed price from a local roofer.
